1. Field of the Invention
The present invention generally relates to system bus control of arbitration between bus requests to use a system bus of a multi-processor system. More particularly, the present invention is concerned with a bus arbiter, a multi-processor system using the same, and a bus control method.
Recently, a data processing system using a multi-processor system has been practically used in order to prevent a system from shutting down and to enable 24-hour operation. In such a system, a bus controller (arbiter) which controls arbitration between bus, requests to use a system bus employs redundant control.
2. Description of the Prior Art
In a conventional concentrated arbitration system, a plurality of processor modules connected to a system bus output external control signals. A bus arbiter, which receives these external control signals, issues a command to one of the processor modules.
Conventionally, if an abnormality occurs, the bus arbiter decodes data transferred via the system and detects the occurrence of abnormality. Then, the bus arbiter stops the operation of the system bus in order to prevent the overall system from being affected by the abnormality. The maintenance operator identifies the abnormality and removes it. Thereafter, the maintenance operator restarts the overall system.
In the above control, the bus arbiter stops the operation of the system bus irrespective of whether or not the abnormality is serious. An example of a serious abnormality is a failure due to breakdown of the hardware in the system. On the other hand, an abnormality, such as a temporary disturbance occurring on the system bus, is not serious. Such a temporary disturbance will occur, for example, if a processor module is added to the system which is operating, or is removed therefrom. Even if an abnormality which is not series occurs, the operation of the system bus is stopped and the maintenance operator restarts the system after the abnormality is identified. Hence, the conventional system does not operate efficiently.